Monica Torres Chancellor of NMSU System Community Colleges | nmsu.edu
Monica Torres Chancellor of NMSU System Community Colleges | nmsu.edu
Southern New Mexico's hot climate poses challenges for those with physically demanding jobs, including migrant farm workers and construction crews. Exercise in such conditions can be more taxing on the cardiovascular system compared to cooler environments. Hillary Yoder, an assistant professor of kinesiology at New Mexico State University (NMSU), is investigating how continuous and interval exercise affect the body in hot conditions. This research is supported by an Emerging Scholars grant from NMSU's College of Health, Education, and Social Transformation.
Yoder joined NMSU in 2022 after earning her Ph.D. from the University of Alabama. She emphasized the importance of understanding how heat impacts exercise: “With increasing frequency and intensity of heat waves, understanding how the body responds to exercise in the heat is of growing importance,” she said. “One reason I became interested in this area of research is the possible practical implications for people who live in hot environments.”
Exercise-induced changes can be monitored through heart rate measurements. In hotter settings, a constant-intensity workout results in increased heart rates while decreasing cardiac output per beat. A phenomenon known as "drift" leads to reductions in VO2 max—maximum oxygen utilization—which makes maintaining exercise intensity feel more challenging.
“What we do not know is if the magnitude of drift is different during continuous compared to interval exercise,” Yoder explained. Her team aims to determine whether continuous or interval exercises cause greater declines in performance.
The study involves participants riding stationary bicycles inside a portable greenhouse set at 95 degrees Fahrenheit with 40% humidity. Participants are healthy adults aged 18-39 who attend five sessions over several weeks. They wear a mouthpiece connected to a metabolic cart that analyzes their breath for oxygen and carbon dioxide levels, measuring VO2 max.
Researchers also examine blood and urine samples before exercising to ensure proper hydration and calculate sweat-induced weight loss post-exercise. Changes in plasma volume are assessed by analyzing red blood cell percentages and hemoglobin levels pre- and post-exercise.
Blood lactate levels provide insight into exertion during VO2 max tests conducted after both interval and continuous exercises; similar lactate levels indicate comparable effort across sessions.
Preliminary findings suggest increases in heart rate and decreased performance after 43 minutes of both types of exercise; however, additional participants are required before drawing conclusions.
“If our hypothesis is correct and interval exercise does increase the amount of cardiovascular drift compared to continuous exercise, then it might be better to complete continuous exercise in hot environments,” Yoder stated.
Following completion, Yoder plans to present findings at an American College of Sports Medicine conference. For further details about this study, contact Yoder via email at hyoder@nmsu.edu.
A version of this article was originally published in Pinnacle magazine's fall 2024 issue from NMSU's College of HEST.
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